Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 050824
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
324 AM CDT SUN JUL 5 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 324 AM CDT SUN JUL 5 2015

UNSTABLE AIRMASS IN PLACE ACROSS THE REGION EARLY THIS MORNING AS
SOUTHERLY FLOW INCREASES WITH THE ARRIVAL OF THE LOW LEVEL JET. WITH
A BROAD MID LEVEL TROUGH NOSING INTO THE CENTRAL DAKOTAS AND A
SURFACE TROUGH STRENGTHENING IN THE HIGH PLAINS...SCATTERED
CONVECTION HAS DEVELOPED IN THE FORECAST AREA WEST OF US 81. SKINNY
ELEVATED CAPE VALUES AROUND 1500 J/KG AND EFFECTIVE SHEAR VALUES OF
40 KT IN THIS AREA WILL KEEP A MARGINAL SEVERE RISK GOING THROUGH A
LITTLE AFTER DAYBREAK WHEN THE LLJ BEGINS WANING SOME. MAIN THREAT
IS HAIL TO HALF DOLLARS AND GUSTS TO 65 MPH...ALONG WITH HEAVY
RAINFALL IN THESE SLOW MOVING STORMS. EXPECT THESE STORMS TO
DIMINISH MID MORNING WITH A BREAK IN THE THUNDERSTORM ACTIVITY
THROUGH THE AFTERNOON. HIGHS TODAY WILL REACH THE MID 80S TO LOWER
90S.

MODELS HAVE SLOWED THE TIMING OF A POTENT FRONT DROPPING SOUTHEAST
THROUGH THE REGION IN CONJUNCTION WITH THE ARRIVAL OF THE MAIN
TROUGH IN THE NORTHERN PLAINS THIS AFTERNOON. FOR TODAY...THE
SOUTHERLY FLOW WILL CONTINUE TAPPING INTO MUCH DEEPER MOISTURE WHILE
INCREASED WARM AIR ADVECTION AHEAD OF THE FRONT CREATES GREATER
INSTABILITY. CAPPING THIS AFTERNOON SHOULD ALLOW ANY STORM
DEVELOPMENT TO HOLD OFF UNTIL THE EARLY EVENING IN OUR WEST WHEN THE
THE FRONTAL BOUNDARY APPROACHES FROM THE NORTHWEST.  MUCAPE VALUES
SURGE TO AROUND 2000 TO 4000 J/KG ACROSS THE FORECAST AREA WITH
STEEP LAPSE RATES AND SHEAR AROUND 30 TO 40 KT. EXPECT A GOOD
POTENTIAL FOR SEVERE STORMS...WITH HAIL TO 2 INCHES IN DIAMETER AND
GUSTS TO 70 MPH POSSIBLE EARLY IN THE EVENT THIS EVENING...
TRANSITIONING TO MAINLY A WIND EVENT AFTER MIDNIGHT - AS THE STORMS
MOVE INTO THE I29 CORRIDOR AND EASTWARD. WITH VERY HIGH CLOUD BASES
EXPECTED...THE TORNADO THREAT IS LOW. PRECIPITABLE WATER VALUES WILL
BE SEASONALLY SIGNIFICANT - AROUND 1.75 TO 2 INCHES...SO HEAVY
RAINFALL WILL ALSO BE LIKELY WITH THUNDERSTORM ACTIVITY.  STORMS
WILL BE PROGRESSIVE AND FLASH FLOOD GUIDANCE IS PRETTY HIGH...SO
FLASH FLOODING IS LESS OF A CONCERN. WHILE CONVECTION IS
LIKELY...THERE IS SOME CONCERN ABOUT HOW MUCH OF AN IMPACT - IF ANY -
THIS EARLY MORNING CONVECTION WILL HAVE ON OUR POTENTIAL
HEATING/INSTABILITY THIS AFTERNOON AND EVENING.


.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 324 AM CDT SUN JUL 5 2015

LINGERING CONVECTION MAY BE SITUATED OVER THE SOUTHEASTERN PORTIONS
OF THE CWA ON MONDAY MORNING...BEFORE PUSHING OUT BY LATE MORNING AS
THE FRONTAL BOUNDARY FINALLY CLEARS THE AREA. OTHERWISE...THE
REMAINDER OF THE DAY WILL SEE DECREASING CLOUDS AND BREEZY NORTHWEST
WINDS. IT WILL BE COOLER WITH HIGHS IN THE MID AND AND UPPER 70S.
MONDAY NIGHT WILL SEE TEMPERATURES BELOW NORMAL WITH COLD AIR
ADVECTION CONTINUING...WITH LOWS IN THE LOWER TO MID 50S.

SURFACE HIGH PRESSURE BUILDS INTO THE NORTHERN PLAINS ON
TUESDAY...AND WITH A REINFORCING SHOT OF COOLER AIR GRAZING OUR
NORTHEASTERN ZONES HIGH WILL RANGE FROM THE LOWER 70S THROUGH
SOUTHWESTERN MINNESOTA...TO THE UPPER 70S ALONG THE MISSOURI RIVER
CORRIDOR. BY WEDNESDAY A SOUTHERLY FLOW RETURNS TO THE AREA AS THE
HIGH PUSHES OFF TO THE EAST. MODELS ARE INDICATING CONVECTION
DEVELOPING OVER WESTERN SOUTH DAKOTA ON TUESDAY NIGHT AS A SHORTWAVE
BEGINS TO TRACK THROUGH THE AREA. THERE IS THE POSSIBILITY THAT SOME
OF THIS CONVECTION COULD TRACK INTO OUR AREA ON WEDNESDAY.

THE THEME FOR THE REMAINDER OF THE EXTENDED PERIOD IS WARMING
TEMPERATURES THROUGH THE END OF NEXT WEEK. PERIODIC SMALL CONVECTIVE
CHANCES ARE HARD TO PIN DOWN...THOUGH THERE IS SOME CONSENSUS THAT
FRIDAY NIGHT MAY HOLD A SLIGHTLY BETTER CHANCE AS A SHORTWAVE SLIDES
ACROSS THE REGION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1108 PM CDT SAT JUL 4 2015

VFR CONDITIONS WILL DOMINATE THROUGH MOST OF THIS TAF PERIOD. WILL
BE WATCHING FOR ISOLATED STORM THREAT WEST OF I-29 THROUGH THE
EARLY MORNING HOURS...BUT EXPECTED ISOLATED COVERAGE AND LIMITED
CONFIDENCE IN DEVELOPMENT PRECLUDE MENTION IN THE TAFS. GREATER
STORM THREAT WILL MOVE INTO THE FAR NORTHWEST AREAS AGAIN TOWARD
THE END OF THIS TAF PERIOD...AND WILL INTRODUCE MVFR CONDITIONS WITH
THUNDERSTORMS AT KHON AFTER 03Z-04Z.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...
LONG TERM...JM
AVIATION...JH


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